1. Field of the Invention
The present invention relates to a data transmitting apparatus for convolutional coding data on a transmitter side and for decoding data on a receiver side, and relates to a data transmitting method.
2. Description of the Related Art
In the data communications via a radio communication network, since a bit error frequently occurs, an error correction processing must be performed. As one of error correction methods, there is a method in which coding data obtained by convolutional coding an input bit is decoded by a decoding method on a receiver side.
FIG. 1 is a frame structural view of frame data according to a conventional data transmitting apparatus. In FIG. 1, a tail bit 12 is added to transmitting data 11 for each frame.
FIG. 2 is a frame structural view of data before and after convolutional coding according to the conventional data transmitting apparatus. As shown in FIG. 2, coding data 21 is obtained by convolutional coding frame data obtained by adding the tail bit 12 to transmitting data 11. If a total data length of coding data is below a predetermined frame length, a dummy bit 22 for covering the shortfall is inserted to coding data 21. The transmitter side transmits data having the dummy bit 22 inserted to coding data 21 as a transmitting signal of one unit.
However, in the conventional data transmitting apparatus and data transmitting method, the dummy bit having no information is added to data, which has been convolutional coded. This results in an increase in redundancy, and causes a problem in which a transmission quality cannot be improved.
Moreover, on a receiver side, since the path metric of data, which is used in decoding as a reference, is long, a large number of operations and a large quantity of memory capacity are required. This causes a problem in which the hardware scale of a decoder is increased.